European distributor of a Decent K40 and possible Cohesion board & cooling

Hi there, new user to the K40 brigade, currently own 3 x 10 watt non chinese diodes and I am looking to come over to the C02 side.

Firstly does anyone on here please know of a good supplier of K40 base machines here in europe and has some links please and secondly is the Cohesion board sent from America or can it be sent from europe at all .

I understand there are cheaper boards but I want if possible a straight drop in board and I dont want to tinker too much with the cabling if thats possible apart from making it safe which I am ok on, it just on the low voltage side that I did not study electronics. 240 V ac no problems. I can PAT test the item and make sure the high voltage circuit and 240 volts circuits are ok but I am not sure about wiring up any low voltage electronics.

I understand I think from reading on the site that I would need to be looking for a analog model rather than a digital readout K40.

Finally I also come from the land of CNC and use a water cooled spindle on a closed loop radiator and fan system with a reservoir of 3 litres of coolant which works very well.

Is this possible on the K40 or do you need a cold water unit, I am not sure how high the water temperature gets going through the tube and whether I would need a proper cooling system or similar closed loop like my CNC or stick to the drum and submersible pump method.

Many thanks


I don’t know of an EU supplier of K40s, but most of us here in the US just order them straight from China anyways. The analog model is definitely the superior one IMO, but the digital model can be converted to analog for about $20 US.

The Cohesion3D board ships from the US only and there are no EU suppliers at this time.

The closed loop radiator/fan solution you describe might work for the laser as well, but there are a couple things you need to understand regarding its use: the conductivity of the water really matters. You will want to use distilled water only (with no additives) and ensure the water path stays clear of any untreated/uncoated metal. Metal ions will dissolve and enter the distilled water, increasing its conductivity. The higher the conductivity, the higher your risk of arcing inside the tube (which could cause immediate and catastrophic tube and/or power supply failure).

That said, the cooler you keep the tube (and water), the more consistent the tube will operate and the longer it will last. I use appx. 8L in my K40, and the side of the bucket gets warm - but not unacceptably so - to the touch after about an hour of laser tube operation. With my 65W Boss Laser, I use 12L, and it gets a lot warmer. I’m considering purchasing a refrigerant water chiller setup for the Boss since it gets used a lot harder and more often. I haven’t really investigated options there yet.



Thank you very much for your detailed reply, I appreciate it. I’m not sure how it happens in the US but in Europe because of strict VAT and controls on imports etc pretty much anything we order from outside the EU we get caned on for taxes and a laser from china would be almost double the price if I ordered it from ali express or similar.

Having said that I can pick up one for about 285 euros from eBay here in europe , the ones on Amazon are at least 450 and look exactly the same as the ones on eBay , we get the same protection from eBay as Amazon so if its no good you get your money back.

Can I please ask a few questions,

How would I know that I am getting a genuine analog 40 watt, I understand that some people are selling a 30 watt as a 40 Watt, Is there a measurement of a genuine 40 watt I could use to make sure I’m not getting ripped off please with a small 30 watt tube machine.

secondly I understand that there is a slightly cheaper board but limits the axis to two but is a drop in and that is the Mini Gerbil, do you have any comments on that please? I have heard there are lots of issues about the MKS and the smoothie board people are unhappy because MKS I believe have cloned and ripped off the smoothie board and are offering these around the 40 euro mark, I dont want to go down that route simply as I assume the support would be limited from the community,

I have looked to see if there are any smoothie boards but cant find any at the moment so its MKS, Mini gerbil or Cohesion. in reality the last two.

Thirdly, could the cohesion board be used later in a more powerful laser? say a 60 Watt or even a 100 Watt or is it limited to the K40 only? I am only thinking for when i outgrow the K40 and dont want to spend 200 on a board plus all the import duties etc if it only works on the K40.

and finally thank you for your information on the cooling, I wasn’t aware of that apart from the distilled water so I would not go down the closed loop cooling being a newbie on these lasers yet I think. It would probably be better to just stick to large tub and distilled high quality water.

I already have a decent system of ventilation in my workshop for my diode lasers and it would be a simple matter of connecting in the K40 to the existing system, my extractor fan is at the very end of the run and is outside the house. the pipes are all 5 inch with blast gates My Workbee CNC has its own dust extraction system.

Many thanks for any help you can give please.

Kind regards


The Laserboard is definitely capable of running nearly any type of common CO2 laser, regardless of size or power rating. There are people on this forum who have used it for home-built large format machines (some multi-tube - albeit with custom control circuitry) and commercially-produced lasers in the 200W range. So yes, with enough pictures and wiring diagrams we can make it work in pretty much anything. Your investment in the board is safe. Where it really shines, though, is that it’s pretty much a drop-in replacement for the control board in the K40, and will require much less futzing about trying to get things working. It’s worth it. As far as technical reasons go, it’s also a much more powerful microcontroller Than the Mini Grbl - 120MHz, 32 bit vs 16 MHz, 8 bit, and can support multiple axes with ease. If you get the Grbl and want to add a rotary or Z table to your K40 later, you’ll need a different controller.

As far as determining the 30 vs 40 watt it’s a toss-up. It’s whatever China decided to put in them that day and how fastidious the “engineer” putting them together was. Generally the tubes shipping with them are in fact 40W, but due to cheap optics, poor alignment, or cheaping out on the LPSU, the machines can only achieve 30W at the laser head. The optics and alignment can be fixed inexpensively. My advice is to stick with sellers who have listings with proper spelling, grammar, etc. as they may have taken the time to vet their incoming product a bit better before reselling it.

Also keep in mind that the K40 really is a starter laser. It’s capable of some pretty amazing things, don’t get me wrong, but it definitely has limitations, especially in its stock configuration. It’s more than likely that those other limitations will be more impactful to you than the difference between 30 and 40 watts. To put it in perspective, I’ve never even considered measuring the actual output on mine - as long as it does what I need it to do it’s sufficient. :slight_smile:


Thank you very much for that detailed and very useful information.

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